1. Field of the Invention
This invention relates generally to: apparatuses for the separation of undissolved solids from liquids containing them; liquid purification; to open siphons for liquids, to open siphon filters for liquid/solid separation by filtration using a porous filter medium; to liquid purification devices; to liquid cooling devices; to biological organism filtration or separation devices; to microbiological organism filtration or separation devices; to devices for radiating liquid or liquid with entrained or dissolved solids; to radiation detection devices; to devices for purifying liquids with undissolved solids suspended therein or which float to the top of the liquid; and to processes related to the use of each of these apparatuses.
Liquid-solid separations filtrations, and purifications are important in industry, medicine and the sciences. Such process and apparatus can be divided into two broad categories: (a) those directed to liquid and dissolved solids, and (b) those directed to liquids and undissolved solids. This invention provides, inter alia, a process and apparatus for separating liquid and undissolved solids and a process and apparatus for open siphons for liquids.
2. Description of the Prior Art
Prior art filtration apparatuses are classified as either surface type filters or depth type filters. Surface type filters main filtration mechanism is the direct interception of contaminant particles by filter media which causes an unwanted cake or plug to develop on the filter media. Depth type filters main filtration mechanisms are: (a) direct interception; (b) inertial impaction; or (c) diffusional interception--all of which cause filter media clogging which obstructs (or may eventually prevent) liquid flow, requiring filter media cleaning, removal, or replacement. In these types of prior art filtration, the liquid to be filtered must be moved through the filter media and the contaminant particles must be moved to the filter media in the liquid. The liquid-contaminant mixture is moved across the filter media by means of a differential pressure so that the media can intercept and hold the contaminant particles.
Prior art open siphons are slow and inefficient. With regard to filters, the prior art shows many types, but the prior art known to applicant discloses only processes or apparatuses for which "cake" formation by undissolved solids is a major problem. Cake formations in prior art filters obstruct liquid flow and require cleaning, backwashing, or backflushing, or complete filter element replacement. Traditional filters for undissolved solids have problems caused by clogging or by the formation of a cake of the undissolved solids. The solids or cake clogs the filter and reduces liquid flow. This requires either higher pressures to force liquid past the cake, or mechanisms for mechanical vibration of the filters to dislodge the cake and high pressure air cleaning. Some filters use a backwash or backflush process to dislodge the cake. Eventually clogged filter elements are replaced. Many prior art filters cannot tolerate liquids with a high concentration of solids.
The prior art concept of filtration requires that the filter media stop and hold the contaminants to be filtered. In other words, prior art filters must clog or cake to some extent to provide filtration. Hence, prior art filters must be cleaned or replaced. There is no alternative if they are to provide filtration.
Another concept equally important to prior art filtration is that the fluid to be filtered is forced under pressure through the filter media. This forcing is necessary because as the filter media stops and holds more and more contaminants, more force is required to assure flow of the fluid through the filter. The liquid to be filtered is forced through the filter at a relatively high velocity. The filtered matter is held by the filter material. The velocity of the liquid is sufficient to impart considerable momentum to the contaminant material particles. According to classic filtration principles all the fluid to be filtered must pass through the filter media and all the contaminant particles must pass into and be held by the filter media. In short, prior art filtration requires plugging or caking and forced fluid flow.
Siphons can be classified in two categories: (a) closed siphons and (b) open siphons.
Closed siphons such as conduits, pipes, or housings have walls through which liquid will not pass and are usually configured in an inverted U-shape with an intake end and a discharge end. A hydraulic gradient created by the difference in levels between the intake end and the discharge end causes liquid to flow through the siphon. One drawback of a closed siphon is that its action can be reduced or completely shut-off by the formation of an air pocket within the siphon. In any closed siphon in which the siphon wall extends beneath the surface of a fluid to be siphoned, a pressure differential exists between the surface of the liquid and the siphon intake. Due to this pressure differential there is forced flow of the liquid into the siphon intake which will contribute to the compression of contaminants at the intake.
Open siphons are characterized by the absence of a pre-defined conduit acting as a siphon. Nevertheless, the intake end of an open siphon must pass through the plane of the surface of the liquid. The liquid does not have to be transported further above the liquid surface level by the siphon, but the siphon should intersect the interface between the surface of the liquid and the gas above the liquid. The porous medium is the scaffolding inside of which an envelope of liquid forms. The medium contains multiple interconnected passages. The liquid flows through the medium by siphonage. Above the liquid, the porous medium contacts a gas phase such as vapor of the same liquid, atmospheric gas, or other gases or vapors.
Although normally one would prime the siphon by saturating the porous medium, this is not necessary. Porous media can self-prime. Capillary action raises liquid from the surface of the reservoir into the porous media. Once liquid reaches the top portion, (a very slow process by capillary action) gravity will pull the liquid down toward the outlet end of the medium. At this point, capillary action is overcome by siphonage and liquid flow increases.
The prior art shows apparatus which use porous media for moving, transferring, supplying, or dispensing liquids to lower levels by siphonage. Examples of porous media are: bundles of fibers, matted fibrous or filamentous material, micro-porous membranes, and sorbent material. See U.S. Pat. Nos. 2,770,492; 2,515,569; 2,520,056; and 2,457,851. However, these patents do not deal in any way with filtering or liquid solid separation. They do not address the problem of filtering, they do not solve the problems of filtering, and they do not teach selecting a porous medium that is related to excluding undissolved solids of a given size.
U.S. Pat. No. 4,280,658 to Ehrrich discloses a process and apparatus for liquid cleaning through capillary action. However, Ehrrich does not teach or deal with the separation action of the present invention. His device transports liquid with siphonage, but it filters with capillary action. Filtration takes place at the second vessel where the micro-porous membrane is placed. Capillary action, not siphonage, filters the liquid as it travels through the membrane from the bottom to the surface where it is evaporated. No hydraulic gradient is involved during filtration in Ehrrich's invention.
U.S. Pat. No. 4,126,556 to Swanson discloses an apparatus for removal of an immersed liquid from a liquid mixture. A porous material capable of absorbing the liquid to be separated is positioned as a siphon, and that specific liquid is removed. Although employing the structure of an open siphon, Swanson uses a system capable of siphonage only for transportation. He does not remove solids from a mixture of liquids; he removes one liquid chemical from a mixture of liquid chemicals by using a chemically specific wick. (See column 7, line 1-5) Swanson does not suggest separating all liquids from undissolved solids by using the same medium, nor does he deal with any of the clogging problems found with traditional filters.
U.S. Pat. No. 3,236,768 to Litt discloses a structure which could be taken as an open siphon filter, but it does not suggest or teach the present invention. Litt discloses a process for water purification using a capillary lattice. The lattice in Litt comprises a body or mass which is compacted enough not to have any passages of a size which serve merely as siphon conduits. Water, by capillary diffusion and under gravity, moves inwardly and downwardly through the lattice leaving behind ions collected on the lattice's faces. The lattice is a matted filamentous material compacted so much that it eliminates any passages capable of serving as a siphon conduit. Additionally, Litt deals with separation of ionic particles, i.e., dissolved solids. He never suggests to apply his invention for separation of undissolved solids. He expressly states that heavy or gross solids can be removed by conventional mechanical filters (see for example, column 2, lines 41-44 and column 3, lines 33-35).
The art knows closed siphon filters for liquid purification or separation; for example an abstract obtained of Japanese Patent No. 55116419 dated 80-09-08 describes a method for producing a filtering element for filtering liquids. That patent teaches capillary forming raw material charged in a straight pipe, bent into a U-shape and placed to form an inverted U-shaped solid siphon pipe. Also, Japanese Patent Nos. 55011056 dated 80-01-25 and 54151565 dated 79-11-28 describe closed capillary filters comprising a number of tubes dipped at one end into a bath of liquid to be filtered, each of the tubes being packed by a bundle of filaments to draw the liquid from the bath into the tube by capillary action. They do not disclose open siphon filters.
U.S. Pat. No. 3,236,757 to Litt discloses a method and apparatus for water reclamation which employ a wick which is either substantially or entirely contained within a closed conduit. The wick acts by capillary diffusion to conduct water from one vessel to another. This patent contains no teachings or suggestions regarding siphonage or filtration.
U.S. Pat. No. 3,977,364 to Gijsbers et al discloses an apparatus for evaporating liquids which uses a porous layer acting as a siphon to draw up liquid from a receptacle. This patent contains no teachings regarding filtration.
Closed siphon filters present the same drawbacks as conventional filters. In those filters, a cake of undissolved solid particles is formed at the intake end of the closed siphon, which can plug the closed siphon and obstruct or prevent liquid flow. Consequently, such filters need frequent cleaning and cake removal. The pressure difference obtained by the hydraulic gradient of a siphon makes the closed siphon filter unsuitable for many applications since the cake requires higher pressure differentials for liquid flow. The pressure losses through the cake at the intake end can stop the siphoning action. Conventional filters require pumps or vacuums to create pressure differences high enough to force liquid past clogged areas or cake areas.